Energy Reports 6 (2020) 2627–2640 Contents lists available at ScienceDirect Energy Reports journal homepage: www.elsevier.com/locate/egyr Sustainable biomass pellets using trunk wood from olive groves at the end of their life cycle Víctor M. Soltero a,∗ , Lidia Román a , M. Estela Peralta a , Ricardo Chacartegui b a Department of Design Engineering, University of Seville, 41011 Seville, Spain b Department of Energy Engineering, University of Seville, 41092 Seville, Spain article info Article history: Received 19 September 2019 Received in revised form 4 September 2020 Accepted 19 September 2020 Available online xxxx Keywords: Sustainability Biomass Biofuel Pellets Olive tree management abstract Forest biomass is the raw material most commonly used to produce quality pellets for domestic households. However, sustainable forest biomass is not available in all regions, but there are other potential raw material sources for biomass heating systems, based on pellets. There are a large number of olive trees in the Mediterranean area, but these are not used as renewable pellet fuel because the bark cannot be used as raw material to produce quality pellets. The aim of this study is to carry out a methodology to estimate the optimal sustainable bioenergy life cycle, and the amount of sustainable residue available (trunk wood) at the end of the life of the olive grove, by optimizing the benefits, through an analysis of costs and income of the whole life process. The methodology determines the potential value of the trunks of olive trees to be used as biomass, in the form of pellets in domestic contexts and in a specific geographical area. In a case study applied to Andalusia, it has been shown that the optimal renewable life-cycle is 97 years. If policies for agricultural and energy sustainability favouring this model were adopted, this region would produce 160,000 tonnes of pellets per year, and 266,500 tonnes per year, if extended to the whole of Spain. This has a potential for providing 70.17% of the current total pellet consumption. The extension of the model to other Mediterranean countries, such as Greece and Italy, would result in an additional 124,000 and 144,000 tonnes of pellets per year, respectively. © 2020 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/). 1. Introduction Energy, as a resource, is one of the main indicators of the human development index level (Gouveia et al., 2019; Insah and Bhattacharyya, 2015; Neumayer, 2001). Currently, 77.6% of the European energy supply comes from fossil fuels, whereas 11.7% is supplied by nuclear plants, and 11.1% comes from renewable energy sources. This high dependence on fossil resources pro- duces significant environmental impacts and affects the economy. It motivates policies for promoting the development and use of renewable alternative sources. In the case of the EU-28, the use of renewable energies in 2015 accounted for 16.66% of gross final consumption, compared to 16.13% in 2014. Within these data, regarding the production of heat with biomass, in 2015, bioenergy represented 10% of total energy consumed and 61.34% of the renewable energy used (AEBIOM, 2017), making biofuels currently one of the main renewable energy alternatives. ∗ Corresponding author. E-mail addresses: vmsoltero@us.es, vsoltero@us.es (V.M. Soltero), lidromflo@alum.us.es (L. Román), mperalta1@us.es (M.E. Peralta), ricardoch@us.es (R. Chacartegui). In this context, the use of agricultural, forestry or food residues, for their use in heating systems in buildings and individual dwellings, is a waste management strategy that offers advantages for the circular economy (Valentín et al., 2016) and reduces the dependence on fossil fuels (Agar, 2017; Cheng, 2017). Although it involves combustion and CO 2 emissions, the whole chain will be CO 2 neutral, being compensated throughout the useful life of the agricultural resource by the process of photosynthesis (Anon; Working Group III IPCC, 2007). The development of sustainable strategies and policies based on these raw materials, assuring the economic and technical viability of systems based on their use and exploitation, requires the guarantee of medium and long-term supply, as well as a minimum low heat value (Hoogwijk et al., 2003; Werther et al., 2000). Currently, wood chips, agro-industrial residues, firewood and pellets are the main solid biofuels used for this purpose (Karkania et al., 2012; Waheed et al., 2019). Fig. 1 shows the distribution of pellet production and global trade flows (Calderón et al., 2018). As Fig. 1 shows, Europe is the world’s largest consumer of pellets with 20.3 million tonnes in 2015 (European Biomass As- sociation (AEBIOM), 2016), of which, 6.2 million tonnes were https://doi.org/10.1016/j.egyr.2020.09.017 2352-4847/© 2020 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).